Very high energy gamma-ray emission beyond 10 TeV from GRB 221009A

TL;DR

This paper reports the first detection of gamma-rays up to 13 TeV from GRB 221009A, challenging existing models and suggesting new physics or greater intergalactic transparency.

Contribution

First observation of gamma-rays beyond 10 TeV from a GRB, providing new insights into high-energy emission mechanisms and intergalactic space transparency.

Findings

Detected gamma-rays up to 13 TeV from GRB 221009A

The gamma-ray spectrum is consistent with a power-law after EBL correction

Challenges the synchrotron self-Compton model for TeV afterglow emission

Abstract

The highest energy gamma-rays from gamma-ray bursts (GRBs) have important implications for their radiation mechanism. Here we report for the first time the detection of gamma-rays up to 13 TeV from the brightest GRB 221009A by the Large High Altitude Air-shower Observatory (LHAASO). The LHAASO-KM2A detector registered more than 140 gamma-rays with energies above 3 TeV during 230$-$900s after the trigger. The intrinsic energy spectrum of gamma-rays can be described by a power-law after correcting for extragalactic background light (EBL) absorption. Such a hard spectrum challenges the synchrotron self-Compton (SSC) scenario of relativistic electrons for the afterglow emission above several TeV. Observations of gamma-rays up to 13 TeV from a source with a measured redshift of z=0.151 hints more transparency in intergalactic space than previously expected. Alternatively, one may invoke new physics such as Lorentz Invariance Violation (LIV) or an axion origin of very high energy (VHE) signals.